1. Field of the Invention
The present invention relates to an optical recording and reproducing apparatus for optically recording or reproducing information on a medium, such as an optical disk, and also relates to a tilt correction method, a tilt correction program and a medium.
2. Related Art of the Invention
In the present information-oriented age, technological development of high-density, large-capacity memory devices is proceeding actively. Capabilities required for such memory devices are high density, large capacity, high reliability, a rewritable function and the like. An optical disk is available as a medium capable of satisfying these requirements. The present invention relates to an optical recording apparatus for recording and reproducing information on such an optical disk used as a medium. Conventionally, numerous reports have been made as to the commercialization of optical disks and optical disk apparatuses for recording and reproducing the optical disks, typified by CD, MD and DVD systems, as well as technologies for them.
A DVD system and its drive will be described below as a conventional example referring to the accompanying drawings. FIGS. 7(a) to 7(c) are views illustrating schematic configurations of a digital video disk (DVD) serving as an optical disk and an optical head in an optical disk apparatus for reproducing information on the disk. The configurations and operations of the disk and apparatus will be described below.
In FIG. 7(a), numeral 6a designates a digital video disk (DVD) serving as a medium, i.e., an optical disk. Numeral 1 designates a spindle motor for rotating the DVD (6a) loaded thereon. Numeral 2 designates an optical head having a light-emitting portion and a light-receiving portion. Numeral 3 designates an object lens, mounted on the optical head 2, for condensing light emitted from the light-emitting portion into the information face of the DVD (6a) and thereby forming a light spot. Numeral 4 designates an object lens drive for driving the object lens 3 in a focus direction F and a tracking direction T so that the light spot stably follows the wobbling and eccentricity of the DVD (6a). Numeral 5 designates a drive shaft system for moving the optical head 2 in the radial direction of the DVD (6a).
Since the DVD (6a) is intended for reproduction only, flat land areas L and pit rows P are formed thereon, thereby forming tracks TR as an information face on which pit row information signals are recorded. FIG. 7(b) is a sectional view of the DVD (6a). The cross section shown herein is obtained by cutting the optical disk from its center to its outer circumference in a zigzag form so as to cross the pit rows without fail.
The reproduction operation of the DVD system will be described below. During reproduction on the DVD (6a), the optical head 2 emits DC light having a relatively small power, and a minute light spot is formed on a pit row on the information face by the object lens 3. To cope with wobbling and eccentricity owing to the rotation of the DVD (6a) by the spindle motor 1, the object lens 3 is driven in the focus direction F and the tracking direction T by the object lens drive 4 so as to follow the track and to form a stable light spot. With this configuration, the presence or absence of pits is detected depending on the intensity of the light reflected by pit rows, and information is reproduced as a pit information signal. In addition, by moving the optical head 2 in the radial direction of the DVD (6a) using the drive shaft system 5, it is possible to reproduce information signals in the whole area of the DVD (6a).
If the DVD (6a) has a large warp (tilt), the DVD system cannot stably detect the pit row signal. Generally, such a tilt occurs in the radial direction of the DVD (6a). In this case, by subjecting the drive shaft system 5 to rotation operation A around the axis in the tangential direction (TG) of a predetermined track (TR), the relative angle between the DVD (6a) and the optical head 2, that is, the relative angle between the DVD (6a) and the axis of the outgoing light from the object lens 3 is adjusted so that the pit row information signal can be reproduced with minimal errors. The predetermined track is a track wherein the light spot is formed. The graph of FIG. 7(c) illustrates the reproduction characteristic of the pit row information signal, wherein the abscissa represents the angle of the above-mentioned rotation of the drive shaft system 5, i.e., the amount of the tilt of the DVD (6a), and the ordinate represents the amount of reproduction jitter. By carrying out the rotation operation A of the drive shaft system 5, the relative angle between the DVD (6a) and the axis of the outgoing light of the object lens 3 is adjusted to an angle wherein the amount of reproduction jitter becomes nearly minimal. This adjustment performs the so-called tilt correction. Although the drive shaft system 5 is subjected to the rotation operation A as described above, another system is available wherein the object lens drive 4 has a function of subjecting the object lens 3 to rotation operation B around the axis in the tangential direction (TG) of the above-mentioned predetermined track TR in order to carry out tilt correction. Furthermore, the amount of the tilt for the tilt correction carried out in this way may be an amount of correction fixed beforehand by a drive, or the amount of correction may be determined each time the DVD (6a) is loaded. The configuration of the tilt correction thus differs depending on the drive.
Other components of the drive, that is, components not based on the purpose of the present invention, such as circuits and mechanisms, are not illustrated or explained herein.
The above-mentioned conventional configuration, however, has the following problems.
FIG. 7(a) illustrates a case wherein the DVD (6a) has a large warp (tilt), and the tilt occurs generally in the radial direction of the DVD (6a). In this case, the above-mentioned rotation operation A of the drive shaft system 5 and the above-mentioned rotation operation B of the object lens 3 by the object lens drive 4 are detected depending on the characteristic of the amount of the reproduction jitter shown in FIG. 7(c). Hence, it is necessary to detect the reproduction signal of the disk by carrying out the so-called focus servo-control, tracking servo-control and reproduction characteristic detection. In other words, the tilt correction operation for obtaining an optimum position by carrying out the above-mentioned rotation operations is substantially the same as a series of operations required for ordinary signal reproduction. Hence, the algorithm for the operations becomes complicated. Furthermore, this operation algorithm needs a constant time. For example, when the amount of correction in this tilt correction is fixed beforehand by the drive, a short time may be used at the completion time of drive operation. However, in the case when tilt correction is carried out each time the DVD (6a) is loaded, or when tilt correction is carried out every moment depending on the radial position on the DVD (6a), the proportion of the constant time becomes larger in comparison with the operation time for the function of reproducing an actual information signal. This is equivalent to reduction of the operation function of the drive in view of the usage feeling of a user.
Furthermore, in the conventional configuration, a pit row information signal is present as shown in FIG. 7(b), since the DVD (6a) is intended for reproduction only. However, in the case of a recording optical disk, no information signal is present. Hence, the characteristic of the amount of the reproduction jitter shown in FIG. 7(c), required to be detected for tilt correction, cannot be obtained, thereby causing a problem. To solve this problem, for example, a DVD-RAM system has a format wherein pit rows for tilt correction are provided beforehand on its optical disk itself. However, this kind of countermeasure is not taken for the MD, CD-R, CD-RW and DVD-R systems having already been available commercially. In other words, in the case when a recording optical disk, wherein any countermeasures, such as the pit rows for tilt correction, are not provided beforehand, has a large warp (tilt), tilt correction cannot be carried out, thereby causing a problem of making recording and reproduction unstable.
The present invention is intended to provide a system applicable to all optical disks including reproduction-only types and recording types, and capable of detecting a detection signal for tilt correction without providing any special countermeasures on optical disks and without using any special means and components in the drive, thereby providing an optical recording and reproducing apparatus, a tilt correction method and a tilt correction program not adversely affecting the usage feeling of a user.
One aspect of the present invention is an optical recording and reproducing apparatus for optically recording and reproducing information, comprising:
an optical head having (1) means of condensing light into a medium provided with first areas having dent portions or groove portions and substantially flat second areas, and (2) means of detecting signals from said medium, and
tilt correction means of correcting the relative angle between said medium and the axis of light outgoing from said condensing means of said optical head, wherein
while said medium is subjected to focus servo-control by using a light spot formed by said condensing means, said tilt correction means is operated so that a value based on the difference between the detection level of the reflected light in said first areas and the detection level of the reflected light in said second areas among the detection levels of light reflected by said medium and received and detected by said signal detection means becomes virtually maximal, thereby to correct said relative angle.
Another aspect of the present invention is an optical recording and reproducing apparatus in accordance with 1st invention, wherein said first areas are pit row areas, groove areas or sample pit areas, and
said second areas are flat land areas.
Still another aspect of the present invention is an optical recording and reproducing apparatus, wherein
the fact that said tilt correction means is operated so that said value becomes virtually maximal is understood that said tilt correction means is operated so that the value obtained by the following equation:
|level 2xe2x88x92level 1|/|level 2+level 1|xe2x80x83xe2x80x83[Equation 1]
becomes virtually maximal when said detection level of the reflected light in said first areas is level 1 and when said detection level of the reflected light in said second areas is level 2.
Yet another aspect of the present invention is an optical recording and reproducing apparatus, wherein said medium is an information reproducing medium having tracks wherein said pit row areas used as said first areas and said flat land areas used as said second areas are disposed alternately on a plane, or an information recording medium having tracks wherein said groove areas used as said first areas and said flat land areas used as said second areas are disposed alternately on a plane.
Still yet another aspect of the present invention is an optical recording and reproducing apparatus, wherein said medium is an information recording medium wherein said flat land areas, used as said second areas, for recording information and said sample pit areas, used as said first areas, for detecting a tracking error signal by the sample servo-control method are disposed on a plane.
A further aspect of the present invention is an optical recording and reproducing apparatus, wherein said medium is an information recording medium having said sample pit areas for detecting a tracking error signal by the sample servo-control method, said flat land areas surrounding said sample pit areas and used as said second areas, and groove areas for recording information, and
adjustment is carried out so that the reflected light from either said sample pit areas or said groove areas is detected as the reflected light from said first areas.
A still further aspect of the present invention is an optical recording and reproducing apparatus, wherein said tilt correction means is a condensing means drive that can rotate said condensing means around the axis corresponding to the position of said condensing means the track direction on said medium.
A yet further aspect of the present invention is an optical recording and reproducing apparatus, wherein said tilt correction means is a liquid crystal element mounted on said optical head, having plural areas and being capable of changing the phase distribution of luminous fluxes passing through the respective areas depending on applied voltage.
A still yet further aspect of the present invention is an optical recording and reproducing apparatus, wherein a guide member for moving said optical head is provided, and
said tilt correction means is a mechanism capable of rotating or deforming said guide member around the axis in a direction orthogonal to the movement direction of said optical head.
With the above-mentioned configuration, in the case when the tilt correction means is the above-mentioned condensing means drive, the above-mentioned liquid crystal element or the above-mentioned mechanism, either of these is operated depending on the above-mentioned detected and calculated signal, whereby the relative angle between the medium and the axis of the outgoing light from the condensing means can be controlled properly, and speedy tilt correction can be attained.
An additional further aspect of the present invention is an optical recording and reproducing apparatus for optically recording and reproducing information, comprising:
an optical head having (1) means of condensing light into a medium having tracks wherein pit rows or groove areasm, and flat land areas formed alternately on a plane, and (2) means of detecting signals from said medium, and
tilt correction means of correcting the relative angle between said medium and the axis of outgoing light from said condensing means of said optical head, wherein
while said medium is subjected to focus servo-control by using a light spot formed by said condensing means, and when said signal detection means receives and detects the reflected light from said medium owing to said light spot, said tilt correction means is operated so that a value obtained by the following equation:
|level Lxe2x88x92level G|/|level L+level G|xe2x80x83xe2x80x83[Equation 2]
in the relationship between the level (level G) of the reflected light in said pit rows or said groove areas and the level (level L) of the reflected light in said flat land areas, becomes virtually maximal, thereby to correct said relative angle.
With the above-mentioned configuration, for example, in the case of using a medium having tracks wherein pit rows or groove areas and flat land areas are formed alternately on a plane, in the relationship between the level (level G) of the reflected light in the pit rows or groove areas and the level (level L) of the reflected light in the flat land areas, |level Lxe2x88x92level G|/|level L+level G| is detected and calculated, and the tilt correction means is operated so as to make this value maximal, whereby the relative angle between the medium and the axis of the outgoing light from the condensing means can be controlled properly, and speedy tilt correction can be attained.
A still additional further aspect of the present invention is an optical recording and reproducing apparatus for optically recording and reproducing information, comprising:
an optical head having (1) means of condensing light into a medium wherein flat land areas and sample pit areas for detecting a tracking error signal by the sample servo-control method are formed on a plane, and (2) means of detecting signals from said medium, and
tilt correction means of correcting the relative angle between said medium and the axis of outgoing light from said condensing means of said optical head, wherein
while said medium is subjected to focus servo-control by using a light spot formed by said condensing means, and when said signal detection means receives and detects the reflected light from said medium owing to said light spot, said tilt correction means is operated so that a value obtained by the following equation:
|level Lxe2x88x92level S|/|level L+level S|xe2x80x83xe2x80x83[Equation 3]
in the relationship between the level (level S) of the reflected light in said sample pit areas and the level (level L) of the reflected light in said flat land areas, becomes virtually maximal, thereby to correct said relative angle.
With the above-mentioned configuration, for example, in the case of using a medium wherein flat land areas and sample pit areas for detecting a tracking error signal by the sample servo-control method are formed alternately on a plane, in the relationship between the level (level S) of the reflected light in the sample pit rows and the level (level L) of the reflected light in the flat land areas, |level Lxe2x88x92level S|/|level L+level S| is detected and calculated, and the tilt correction means is operated so as to make this value maximal, whereby the relative angle between the medium and the axis of the outgoing light from the condensing means can be controlled properly, and speedy tilt correction can be attained.
A yet additional further aspect of the present invention is a tilt correction method for correcting the relative angle between a medium and the axis of outgoing light from condensing means in an optical recording and reproducing apparatus for optically recording and reproducing information, comprising an optical head having (1) said condensing means of condensing light into said medium provided with first areas having dent portions or groove portions and substantially flat second areas, and (2) means of detecting signals from said medium, wherein
while said medium is subjected to focus servo-control by using a light spot formed by said condensing means, said relative angle is corrected so that a value based on the difference between the detection level of the reflected light in said first areas and the detection level of the reflected light in said second areas among the detection levels of light reflected by said medium and received and detected by said signal detection means becomes virtually maximal.
A still yet further aspect of the present invention is a tilt correction method, wherein said first areas are pit row areas, groove areas or sample pit areas, and
A supplementary further aspect of the present invention is a tilt correction method, wherein
the fact that said relative angle is corrected so that said value becomes virtually maximal is understood that said relative angle is corrected so that the value obtained by the following equation:
|level 2xe2x88x92level 1|/|level 2+level 1|xe2x80x83xe2x80x83[Equation 1]
becomes virtually maximal when said detection level of the reflected light in said first areas is level 1 and when said detection level of the reflected light in said second areas is level 2.
A still supplementary aspect of the present invention is a program for allowing a computer to function as the whole or part of said tilt correction means of an optical recording and reproducing apparatus.
A yet still supplementary aspect of the present invention is a program for allowing a computer to execute all or part of steps of a tilt correction method.
A still yet supplementary aspect of the present invention is a medium having a program and/or data for allowing a computer to execute all or part of the functions of said tilt correction means of an optical recording and reproducing apparatus, said medium being able to be processed by the computer.
One aspect of the present invention is a medium having a program and/or data for allowing a computer to execute all or part of the operation steps of a tilt correction method, said medium being able to be processed by the computer.
With this configuration, for example, it is possible to provide a system capable of detecting a detection signal for tilt correction without providing any special countermeasures on optical disks and without using any special means and components in the drive, and it is possible to obtain an optical recording and reproducing apparatus not adversely affecting the usage feeling of a user.